EMail attachment size, what is your limit???

[chuntmd_ironport]

MIME encoding sucks :lol:

A email with a 35meg .zip attachment comes in as 49.6megs (using the smtp logs)

I've got a non-tech CTO that want to accept 50meg attachments. It seems to be working but sometimes the SOPHOS AV engine crapsout and the email ends up in the quarantine.

For business to business email what is a reasonable size limit?

[Erich_ironport]

We use 10MB as a standard within Exchange. We have a small handful of systems that use larger attachments so our IronPort limit is 100MB. You know that you can change this based on SenderGroup and SBRS.

One of our issues is that Exchange uses SMTP binary chunking and 8bit to transfer email within the Exchange Org, but the Exchange coverts to 7bit when sending to the IronPort due to the fact the these SMTP extensions are not supported by IronPort yet; so our internal limit is 10MB and external is really closer to 7.5MB. :( - If anyone has more insight as to what the specific issues are here please correct me.

[tminchin_ironport]

We do 100 meg for both internal (Exchange) and external (Ironport).

[Donald Nash]

MIME encoding doesn't suck! What sucks is the fact that we still need to do it. The fact that SMTP is still a 7-bit channel is annoying.

I don't administer an Exchange server myself, but our Exchange admins explained to me that Exchange does size limiting based on the native (aka decoded) size of the attachments. The FreeBSD/qmail server I run enforces the maximum message size based on the wire size, i.e. base64-encoded for anything binary. Since base64 is a 6-in-8 encoding, that increases the object size by 33%. In order to reconcile the size limits on these two systems, the Exchange limit is set to 30 MB and the qmail limit is set to 40 MB. That's usually enough for the PHBs to mail around their humongous PowerPoint presentations.

I haven't bothered messing with the message size limits on our IronPorts, since our back end servers enforce their own limits.

[Corey_ironport]

10Mb in Exchange, 20Mb on IronPort -only to sort of 'filter' the really big stuff that we are never going to accept.